1. Field of the Invention
The present invention relates to a spin transport device in semiconductor spintronics.
2. Related Background Art
In recent years, a phenomenon of spin transport in a semiconductor, particularly silicon (Si), has attracted much attention. Silicon is a key material in current semiconductor products. If silicon-based spintronics can be realized, new functions can be added to a silicon device without discarding existing technology. An example of such a semiconductor spin transport device includes a spin-MOSFET. Semiconductor spin transport devices include a semiconductor spin transport device using both electric current and spin current (magnetoresistance effect type) and a semiconductor spin transport device using only spin current (non-local structure type).
In the non-local structure type semiconductor spin transport device, since a path of the electric current differs from a path of the spin current, and the spin current does not have charge or cause a voltage, an output with high S/N is expected to be obtained. However, in the non-local structure type semiconductor spin transport device, there is a problem in that an output is generally small. In order to increase the output, the inventors of the present application have considered a method of adjusting an impurity concentration in a semiconductor (see Patent Document 1 (Japanese Patent Laid-Open No. 2010-287666)).
In this method, high concentration impurities are added only near a surface of the semiconductor to decrease interfacial resistance, resulting in an improved output.